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US-20260130019-A1 - LIGHT EMITTING DEVICE AND LIGHTING APPARATUS INCLUDING THE SAME

US20260130019A1US 20260130019 A1US20260130019 A1US 20260130019A1US-20260130019-A1

Abstract

A light emitting device is adapted to realize white light and includes a first light emitting diode chip emitting light having a first peak wavelength in the range of 400 nm to 420 nm, a second light emitting diode chip emitting light having a second peak wavelength in the range of 420 nm to 440 nm, and a wavelength converter covering the first and second light emitting diode chips. The wavelength converter including a blue phosphor, a green phosphor, and a red phosphor. When a maximum value of a spectral power distribution of the light emitting device or a maximum of a reference spectral power distribution of black body radiation is 100%, a difference between the spectral power distribution of the light emitting device and the reference spectral power distribution is less than 20% at each wavelength in the wavelength range of 440 nm to 640 nm.

Inventors

  • Bo Yong HAN

Assignees

  • SEOUL SEMICONDUCTOR CO., LTD.

Dates

Publication Date
20260507
Application Date
20251230

Claims (10)

  1. 1 . A light emitting device, comprising: a first light emitter emitting light having a first peak wavelength; a second light emitter emitting light having a second peak wavelength in the range of 420 nm to 440 nm; and a wavelength converter covering the first and second light emitters, the wavelength converter comprising: a first wavelength converter having a first peak wavelength; a second wavelength converter having a second peak wavelength; and a third wavelength converter having a third peak wavelength, wherein, when a maximum value of a spectral power distribution of the light emitting device or a maximum value of a reference spectral power distribution of black body radiation is 100%, a difference between the spectral power distribution of the light emitting device and the reference spectral power distribution is less than 20% at each wavelength in the wavelength range of 440 nm to 640 nm.
  2. 2 . The light emitting device according to claim 1 , wherein a difference between the first peak wavelength of the first light emitter and the second peak wavelength of the second light emitter is 10 nm or more.
  3. 3 . The light emitting device according to claim 2 , wherein the first peak wavelength is in a range of 410 nm to 417.5 nm and the second peak wavelength is in a range of 430 nm to 437.5 nm.
  4. 4 . The light emitting device according to claim 1 , wherein the light emitting device emits light having a color temperature of 5,000 K or more.
  5. 5 . The light emitting device according to claim 1 , wherein the light emitting device emits light having a color temperature of 5,000 K or less.
  6. 6 . The light emitting device according to claim 1 , further comprising a third light emitter emitting light having a third peak wavelength that is longer than the first peak wavelength and shorter than the second peak wavelength.
  7. 7 . The light emitting device according to claim 1 , further comprising a blue light emitter emitting light having a fourth peak wavelength longer than 440 nm.
  8. 8 . The light emitting device according to claim 1 , wherein both rendering index and fidelity index of the light emitting device are 95 or more.
  9. 9 . The light emitting device according to claim 8 , wherein the light emitting device has a graphic index in the range of 95 to 105.
  10. 10 . A lighting apparatus comprising the light emitting device of claim 1 .

Description

CROSS-REFERENCE TO RELATED APPLICATION AND PRIORITY The present application is a continuation of U.S. patent application Ser. No. 18/369,565, filed on Sep. 18, 2023, which is a continuation of U.S. patent application Ser. No. 17/108,251, filed on Dec. 1, 2020, which is a non-provisional patent application claiming the benefit of and priority to U.S. provisional application No. 62/942,251, filed on Dec. 2, 2019, the disclosure of each of which is incorporated herein by its entirety. TECHNICAL FIELD Embodiments of the present disclosure relate to a light emitting device and a lighting apparatus including the same, and more particularly, to a light emitting device using a light emitting diode as a light source and a lighting apparatus including the same. BACKGROUND Most life forms on earth have adapted to work in tune with the sun. The human body has also adapted to sunlight over a long period of time. Accordingly, human circadian biorhythm is known to change with the change of sunlight. Particularly, in the morning, cortisol is secreted from the human body under bright sunlight. Cortisol causes more blood to be supplied to the organs of the body, increasing the pulse and respiration in response to external stimuli, such as stress, thereby causing the body to awaken and prepare for daytime activity. After active physical activity under active sunlight during the daytime, the body secretes melatonin in the evening to reduce the pulse, body temperature and blood pressure of the body, thereby assisting in resting and sleeping. In modern society, however, most people mainly perform physical activities indoors such as in the home or office settings, instead of under sunlight. It is common that, during the daytime, people commonly spend more time indoors than engaging in physical activity outdoors. However, indoor lighting apparatuses generally exhibit a constant spectral power distribution that significantly differs from the spectral power distribution of sunlight. For example, although a light emitting apparatus using blue, green and red light emitting diodes can realize white light through combination of a blue color, a green color, and a red color, the light emitting apparatus exhibits a spectral power distribution having a peak at a particular wavelength rather than a spectral power distribution over a broad wavelength spectrum of visible light like sunlight. FIG. 1 is a graph depicting a spectral power distribution of black body radiation corresponding to several color temperatures on a Planckian locus in the CIE color coordinate system and FIG. 2 is a graph depicting spectral power distributions of white light sources based on typical blue light emitting diode chips corresponding to several correlated color temperatures. Referring to FIG. 1 and FIG. 2, the spectrum of black body radiation like the sun shows higher intensity in the blue wavelength region with increasing color temperature, as in the spectrum of a typical white light source. However, as color temperature increases, the difference between the spectrum of the white light source and the spectrum of the black body radiation becomes clearer. For example, the spectrum of the black body radiation at a temperature of 6,500K shows that the intensity of light gradually decreases from the blue wavelength region to the red wavelength region. Conversely, as shown in FIG. 2, in the white lighting apparatus based on the blue light emitting diode chips, the intensity of light in the blue wavelength region becomes stronger with increasing color temperature. The human eye lens adapted to the spectrum of sunlight can be damaged by abnormally strong light in the blue wavelength region, thereby causing poor eyesight. Moreover, when retinal cells are exposed to excessive energy in the blue wavelength region, abnormal signals can be transmitted to the brain, thus abnormally promoting or suppressing generation of hormones, such as cortisol and melatonin. This may have a negative effect on the body's circadian rhythm. In recent years, various studies have been made to develop a white light source having a similar spectral power distribution to sunlight. In particular, a technique for reducing the intensity of light in the blue wavelength region through combination of a UV or violet light emitting diode and blue, green and red phosphors has been developed. However, the white light source based on such combination causes various drawbacks. First, luminous efficacy may deteriorate. Since the white light source requires wavelength conversion of light for a greater quantity of phosphors than typical light sources, deterioration in efficiency due to wavelength conversion occurs. Moreover, since the blue phosphor has characteristics of reflecting light, the amount of the blue phosphors is increased in order to obtain the intensity of blue light, thereby causing further deterioration in efficiency of wavelength conversion. Moreover, light emitted from the green or red phosphors